1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a structure of a liquid crystal display module having a supporting frame in a backlight device.
2. Discussion of the Related Art
Liquid crystal displays (LCDs) are gaining in popularity for use in systems such as television receivers, computer monitors, avionics displays, aerospace displays, and other military-related displays where the elimination of cathode ray tube (CRT) technology is desirable for several reasons. In particular, CRTs are characterized by large depth dimensions, undesirably high weight, and fragility. Additionally, CRTs require a relatively high voltage power supply in order to sufficiently accelerate electron beams for displaying images.
The aforementioned shortcomings of CRTs are overcome by flat panel liquid crystal displays in which matrix arrays of liquid crystal picture elements or pixels are arranged in a plurality of rows and columns. In general, LCD devices have various advantages in that they are thin, and consume little power, and so on, in comparison with CRT display devices. Therefore, such LCD devices might be expected to be substituted for CRT display devices and have been a matter of great interest in some industry fields.
In contrast to the CRT, the liquid crystal display device requires a light source because the liquid crystal is not fluorescent material. Therefore, as the light source lamp, a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL) or the like is used. Moreover, there are a few kinds of backlight units such as a direct backlight type (or direct type) unit and an edge light type unit.
A direct backlight type surface light source device generally reflects light from a light source onto the back surface of a liquid crystal panel or the like by means of a reflective plate, and diffuses its output light by means of a light diffusing sheet disposed at the light outputting surface side so that the shape of the light source cannot be identified by human eyes. An edge light type surface light source device receives light inputted into it from a light source usually through one side end surface of a plate-shaped light guide means of a transparent acryl resin or the like. The edge light type surface light source device leads the light to a light outputting surface which is the other surface of the light guide means, and therefrom outputs the light to the back surface of a liquid crystal panel or the like. In such a case, in order to improve the efficiency of utilizing light, an optical reflective plate or an optical reflective film is often provided on the opposite surface of the light guide means to the light outputting surface and in order to make the output light uniform, a light diffusing sheet having a light diffusing function is often provided at the light outputting surface side of the light guide means.
The reference is explained hereinafter referring to the edge light type surface light source device.
FIG. 1 is a plan view illustrating a large general LCD module, and FIG. 2 is a cross-sectional view taken along line II—II of FIG. 1. As shown in FIGS. 1 and 2, the LCD module 10 generally includes: a liquid crystal (LC) panel 20 comprising two substrates and an interposed liquid crystal layer; a panel guide 30 guiding the LC panel 20; a TCP (Tape Carrier Package) 28 including integrated circuit (IC) chips 26; a PCB (Printed Circuit Board) 32 connected to the pad of the LC panel 20 through the TCP (Tape Carrier Package) 28; a backlight device 40 positioned under the LC panel 20; a top frame 70 supporting the LC panel 20, and a supporting frame 80. The top frame 70 is made of metallic material, and the supporting frame 80 is made of molded plastic.
The supporting frame 80 holds the liquid crystal display device and houses a reflective sheet 42, a light guide plate 44, a light diffusing sheet 46, a prism sheet 48 and a protection sheet 50. The fluorescent lamp with a diameter of a few millimeters is installed at one or both ends of the light guide plate 44. The light guide plate 44 serves to uniformly direct light from the lamp to the LC panel 20, and it is usually made of a transparent acryl having a thickness of a few millimeters. The light guide plate 44 also has a plurality of convex or concave hole dots or a plurality of V-shaped convex or concave bars in order to uniformly reflect and diffuse the light. The reflective sheet 42 is arranged under the light guide plate 44 and upwardly reflects the light from the light guide plate 44. The prism sheet 48 and light diffusing sheet 46 over the light guide plate 44 can be two or three sheets. The prism sheet 48 and the light diffusing sheet 46 gather or diffuse the light in order to improve the brightness and to increase the range of vision. The protection sheet 50 protects the sheets from particles and from scratches. The protection sheet 50 also prevents the sheets from swinging when conveying the backlight device assembly.
In the LCD module 10 described above, a process of aligning the backlight device 40 to the supporting frame 80 will be explained hereinafter. First, the lamp is installed alongside the supporting frame 80. After that, the reflective sheet 42, which is made of polyester, is assembled in order to reflect the light upward. The light guide plate 44 is then assembled over the reflective sheet 42 in order to uniformly reflect the light irradiated from the lamp. The light diffusing sheet 46, which diffuses the light, and the prism sheet 48, which gathers the light, are assembled. Then, the light guide plate 44 and the sheets are fastened by the tapes, by the air pad, and by the protrusion of the supporting frame 80.
Meanwhile, the number of lamps is increased in the conventional art in order to improve the brightness of the large LCD device, and thus the power consumption increases. However, some problems occur in the LCD device because of the heat from the lamp and from the PCB 32. Thus, in order to solve the problems caused by the heat, the supporting frame 80 is made of the metallic material such as aluminum (Al) that has a good thermal conductivity and a good thermal radiation. And then, the supporting frame 80 is installed in the bottom side of the lamp housing and in the vertical side portion of the lamp housing. Moreover, a heat emitting plate (not shown) is connected to the lamp housing of the backlight device 40 as a means of emitting heat such that heat is emitted from the LCD device.
However, the reflective sheet 42 directly contacting the supporting frame 80 is badly affected by the internal heat from the lamp and PCB 32 and by the external heat occurring in operation and maintenance tests at high temperature, because the internal and external heat is emitted from the supporting frame 80 that is made of metallic material. Especially, wrinkles occur in the reflective sheet 42, and thus there are stains in the display area in an operating mode. Therefore, deterioration of the LCD device arises.